High power microwaves can break down a gas to produce electrons and ions, and the ionization process is enhanced by also applying a magnetic field. This is the basis for microwave electron cyclotron resonance (ECR) ion sources. --David B. Miller and George W. Bethke, "Cyclotron Resonance Thruster Design Techniques," AIAA J, 4(5), 835-840 (1966). In semiconductor manufacture, microwave ECR ion sources have been applied to the plasma etching and ion implanting of substrates. In such sources, an etching gas is fed into a microwave waveguide plasma production region which is itself within the magnetic field region. Microwave power is introduced into the waveguide resulting in an ECR discharge from which the etching or implanting ion beam is obtained. --Keizo Suzuki, et al, "Microwave Plasma Etching," Jap. J. of App. Physics, 16(11), 1979-1984 (1977). --Seitaro Matsuo and Yoshio Adachi, "Reactive Ion Beam Etching Using a Broad Beam ECR Ion Source," Jap. J. of App. Physics, 21(1), L4-L6 (1982). --Noriyuki Sakudo, et al, "High-Current Ion Implanter Using a Microwave Ion Source," Rev. Sci. Instrum. 54(6), 681-684 (1983).
In the field of plasma physics, a particular type of plasma confinement known as the magnetic multipole is known for its ability to produce a quiescent and uniform large-area plasma. --Rudolf Limpaecher and K. R. MacKenzie, "Magnetic Multipole Containment of Large Uniform Collisionless Quiescent Plasmas," Rev. Sci. Instrum. 44(6), 726-731 (1973). A line cusp magnetic multipole configuration was used in the 1970's to improve the plasma density and uniformity of the Oak Ridge National Laboratory duoPIGatron ion source. --C. C. Tsai et al, "DuoPIGatron Ion Source for PLT Injectors," Proc. of the 7th Symp. on Eng. Problems of Fusion Research, IEEE Pub. No. 77CH1267-4-NPS, 278-283 (1977). --W. L. Stirling, C. C. Tsai, and P. M. Ryan, "15 cm duoPIGatron Ion Source," Rev. Sci. Instrum. 48(5), 533-536 (1977).
In 1984, a filament-emission line cusp magnetic multipole device was applied to plasma etching. --Thomas D. Mantei, U.S. Pat. No. 4,483,737 (Nov. 20, 1984). Also in 1984, microwave ECR sources began to be combined with magnetic multipoles, with the possibility of applying the technology to large scale plasma etching being immediately recognized. --L. Pomathiod, et al, "Microwave Excitation of Large Volumes of Plasma at Electron Cyclotron Resonance in Multipolar Confinement," Physics Letters, 106A(7), 301-304 (1984). --Y. Arnal, et al, "Plasma Etching in Magnetic Multipole Microwave Discharge," Appl. Phys. Lett 45(2), 132-134 (1984).
In 1988, a distributed ECR source appeared which injected the microwave energy into the line cusps of a magnetic multipole by means of multiple tubular applicators. --Rudolf R. Burke and Claude Pomot, "Microwave Multipolar Plasma for Etching and Deposition," Solid State Technology, 67-71 (Feb. 1988). --Michel Pichot, Jacques Pelletier, and Yues Arnal, U.S. Pat. No. 4,745,337 (May 17, 1988). --RCE 160: The Microwave DECR Reactor, Product Bulletin, ALCATEL DVM, France (May 1988). Again in 1988, there appeared a plasma generating apparatus which utilized permanent magnets in the microwave launcher; Yoshimi Hakamata, "Plasma Generating Apparatus", European Patent Application No. 0 286 132 (Filed Apr. 8, 1988).
A recent paper describes apparatus which combines an ECR source chamber with a multipole magnet structure. --Thomas D. Mantei, "High Density Plasmas for Semiconductor Processing," Proc. 7th Symp. on Plasma Processing, 173rd Mtg. of the Electrochemical Society, Atlanta (1988).
In addition to this prior art, various other plasma generating devices are known. Some of these are: --Jes Asmussen, "Electron Cyclotron Resonance Microwave Discharges for Etching and Thin Film Deposition," to be published as Chapter 11 of Plasma-Based Processing, edited by S. M. Rossnagel, J. J. Cuomo and W. D. Westwood, Noyes Pub. N.J. in 1989. --Davod J. Drage and Toufic Safi, U.S. Pat. No. 4,857,138 (Aug. 15, 1989). --Akihisa Yoshida, et al, U.S. Pat. No. 4,859,908 (Aug. 22, 1989).